Liquid ejection apparatus

Abstract

There is provided a liquid ejection apparatus including: a liquid ejection head that includes nozzles; a signal output circuit that outputs a signal that varies depending on whether at least part of the nozzles includes a discharge-defective nozzle; and a controller. The controller is configured to discharge a liquid on a medium by using a partial discharge mode; perform determination, for at least one nozzle included in the nozzles based on the signal from the signal output circuit, about whether the discharge-defective nozzle is included therein; and set, based on the signal from the signal output circuit, the part of the nozzles not to include the discharge-defective nozzle when the liquid is discharged from the liquid ejection head on the medium by using the partial discharge mode and when the controller has determined that the discharge-defective nozzle is included in the nozzles.

What is claimed is: 
     
       1. A liquid ejection apparatus configured to eject a liquid on a medium, the apparatus comprising:
 a liquid ejection head including a plurality of nozzles arranged in a predefined direction; 
 a signal output circuit configured to output a signal that varies depending on whether at least part of the plurality of nozzles includes a discharge-defective nozzle of which discharge performance is lower than a predefined discharge performance; 
 a discharge mechanism configured to perform a discharge operation in which the liquid in the liquid ejection head is discharged from the plurality of nozzles; and 
 a controller configured to:
 control the liquid ejection head to discharge the liquid on the medium by using a partial discharge mode in which the liquid is discharged from part of the plurality of nozzles; 
 perform determination, for at least one nozzle included in the plurality of nozzles based on the signal from the signal output circuit, as to whether the discharge-defective nozzle is included therein; 
 set, based on the signal from the signal output circuit, the part of the plurality of nozzles to exclude the discharge-defective nozzle in a case that the liquid is discharged from the liquid ejection head on the medium by using the partial discharge mode and the controller has determined that the discharge-defective nozzle is included in the plurality of nozzles; 
 control the liquid ejection head to discharge the liquid on the medium by selectively using either of the partial discharge mode or an entire discharge mode in which the liquid is discharged from all the plurality of nozzles; 
 in a case that the liquid is discharged from the liquid ejection head on the medium by using the entire discharge mode and that the controller has determined that the discharge-defective nozzle is included in the plurality of nozzles, control the liquid ejection head to discharge the liquid from the plurality of nozzles on the medium after the discharge operation of the discharge mechanism; and 
 in the case that the liquid is discharged from the liquid ejection head on the medium by using the partial discharge mode and that the controller has determined that the discharge-defective nozzle is included in the plurality of nozzles,
 set the part of the plurality of nozzles not to include the discharge-defective nozzle, and 
 control the liquid ejection head to discharge the liquid from the part of the plurality of nozzles on the medium without the discharge operation of the discharge mechanism. 
 
 
 
     
     
       2. The liquid ejection apparatus according to  claim 1 , wherein the controller is configured to perform the determination, for all the plurality of nozzles based on the signal from the signal output circuit, about whether the discharge-defective nozzle is included therein. 
     
     
       3. The liquid ejection apparatus according to  claim 1 , wherein the predefined discharge performance is one of a discharge performance as to whether an ink droplet of a predetermined size is discharged from a nozzle, a discharge performance as to whether the ink droplet is discharged at a predetermined speed, and a discharge performance as to whether the ink droplet is discharged in a predetermined direction. 
     
     
       4. The liquid ejection apparatus according to  claim 1 , wherein the partial discharge mode is a mode by which the liquid ejection head discharges the liquid from the part of the plurality of nozzles arranged continuously in the predefined direction. 
     
     
       5. The liquid ejection apparatus according to  claim 4 , further comprising a memory configured to memorize information of a plurality of nozzle groups each formed by the part of the plurality of nozzles arranged continuously in the predefined direction,
 wherein in the case that the liquid is discharged from the liquid ejection head on the medium by using the partial discharge mode and in a case that the controller has determined that the discharge-defective nozzle is excluded in a plurality of first nozzles included in the plurality of nozzle groups and included in a first nozzle group, the controller is configured to set the plurality of first nozzles as the part of the plurality of nozzles, 
 in the case that the liquid is discharged from the liquid ejection head on the medium by using the partial discharge mode, in a case that the controller has determined that the discharge-defective nozzle is included in the plurality of first nozzles, and in a case that the controller has determined that the discharge-defective nozzle is excluded in a plurality of second nozzles included in the plurality of nozzle groups and belonging to a second nozzle group different from the first nozzle group, the controller is configured to set the plurality of second nozzles as the part of the plurality of nozzles. 
 
     
     
       6. The liquid ejection apparatus according to  claim 4 , wherein in the case that the liquid is discharged from the liquid ejection head on the medium by using the partial discharge mode and in a case that the controller has determined that the discharge-defective nozzle is not included in a plurality of first nozzles included in the plurality of nozzles and arranged continuously in the predefined direction, the controller is configured to set the plurality of first nozzles as the part of the plurality of nozzles,
 in the case that the liquid is discharged from the liquid ejection head on the medium by using the partial discharge mode and in a case that the controller has determined that the discharge-defective nozzle is included in the plurality of first nozzles,
 the controller is configured to set, as the part of the plurality of nozzles, one first nozzle that is included in the plurality of first nozzles and that is not the discharge-defective nozzle or part of the plurality of first nozzles that exclude the discharge-defective nozzle and that are arranged continuously in the predefined direction, and a second nozzle that is included in the plurality of nozzles, that is not the discharge-defective nozzle, and that is arranged continuously from the part of the plurality of first nozzles in the predefined direction. 
 
 
     
     
       7. The liquid ejection apparatus according to  claim 5 , further comprising a conveyer configured to convey the medium in a conveyance direction; and
 a carriage carrying the liquid ejection head and configured to move in a scanning direction orthogonal to the conveyance direction, 
 wherein the plurality of nozzles are arranged in the conveyance direction. 
 
     
     
       8. The liquid ejection apparatus according to  claim 7 , wherein the conveyer includes a roller pair disposed downstream of the liquid ejection head in the conveyance direction and configured to convey the medium having a sheet shaped in the conveyance direction while nipping the medium, and
 the plurality of first nozzles are included in the plurality of nozzles and are disposed at a downstream side of the plurality of nozzles in the conveyance direction. 
 
     
     
       9. The liquid ejection apparatus according to  claim 7 , wherein the conveyer is configured to selectively convey, as the medium, either of a first sheet or a second sheet into which the liquid landing thereon is less likely to permeate compared to the first sheet,
 the conveyer includes:
 a roller pair disposed downstream of the liquid ejection head in the conveyance direction and configured to nip and convey the sheet in the conveyance direction, and 
 a holding member disposed upstream of the liquid ejection head in the conveyance direction and configured to hold a facing surface of the sheet that is capable of facing the liquid ejection head, 
 
 in a case that the sheet is the first sheet, the plurality of first nozzles are nozzles included in the plurality of nozzles and disposed at a downstream side of the plurality of nozzles in the conveyance direction, and 
 in a case that the sheet is the second sheet, the plurality of first nozzles are nozzles included in the plurality of nozzles and disposed at an upstream side of the plurality of nozzles in the conveyance direction. 
 
     
     
       10. The liquid ejection apparatus according to  claim 7 , wherein in the case that the controller has determined that the discharge-defective nozzle is included in the plurality of first nozzles, the number of the nozzles set as the part of the plurality of nozzles is smaller than the number of the plurality of first nozzles. 
     
     
       11. The liquid ejection apparatus according to  claim 5 , wherein the liquid ejection head includes a black nozzle row and a color nozzle row, the black nozzle row being formed by a plurality of black nozzles arranged in the predefined direction and from which a black ink is discharged, the color nozzle row being formed by a plurality of color nozzles arranged in the predefined direction, from which a color ink is discharged, and being positioned adjacent to the black nozzle row in a direction orthogonal to the predefined direction,
 the controller is configured to control the liquid ejection head to discharge the liquid on the medium by using, as the partial discharge mode, a discharge mode using both portions in which ink is discharged both from part of the plurality of black nozzles and from part of the plurality of color nozzles having a position in the predefined direction identical to that of the part of the plurality of black nozzles, 
 in a case that the liquid is discharged from the liquid ejection head on the medium by using the discharge mode using both portions, in a case that the controller has determined that the discharge-defective nozzle is excluded in a plurality of first black nozzles included in the plurality of black nozzles arranged continuously in the predefined direction, and in a case that the controller has determined that the discharge-defective nozzle is excluded in a plurality of first color nozzles included in the plurality of color nozzles and having positions in the predefined direction identical to those of the plurality of first black nozzles, the controller is configured to set the plurality of first black nozzles as the part of the plurality of black nozzles, and set the plurality of first color nozzles as the part of the plurality of color nozzles, and 
 in a case that the liquid is discharged from the liquid ejection head on the medium by using the discharge mode using both portions, and in a case that the controller has determined that the discharge-defective nozzle is included in at least any of the plurality of first black nozzles and the plurality of first color nozzles,
 the controller is configured to set, as the part of the plurality of black nozzles, a plurality of second black nozzles included in the plurality of black nozzles, arranged continuously in the predefined direction, not including the discharge-defective nozzle, and corresponding to a plurality of color nozzles that are included in the plurality of color nozzles and that exclude the discharge-defective nozzle and of which positions in the predefined direction are identical to those of the plurality of second black nozzles, and 
 the controller is configured to set, as the part of the plurality of color nozzles, a plurality of second color nozzles included in the plurality of color nozzles and having positions in the predefined direction identical to those of the plurality of second black nozzles. 
 
 
     
     
       12. The liquid ejection apparatus according to  claim 11 , wherein the controller is configured to control the liquid ejection head to discharge the liquid on the medium by selectively using, as the partial discharge mode, either of the discharge mode using both portions or a discharge mode using one portion in which the color ink is discharged from the part of the plurality of color nozzles and the black ink is not discharged from the plurality of black nozzles,
 in a case that the liquid is discharged from the liquid ejection head on the medium by using the discharge mode using one portion, in the case that the controller has determined that the discharge-defective nozzle is included in the plurality of first black nozzles, and in the case that the controller has determined that the discharge-defective nozzle is excluded in the plurality of first color nozzles, the controller is configured to set the plurality of first color nozzles as the part of the plurality of color nozzles.